how to build an acid resistant hood & scrubber

[lazersteve]

Valkyrie,

Are you sure you purchased lye, sodium hydroxide, and not lime, calcium hydroxide and magnesium hydroxide?

They both should work, but I've never seen sodium hydroxide lye for sale in a Lowes store in 40lb bags. It's typically sold in 1 lb cans in the plumbing isle if your store carries it. My local Lowes quit carrying the Red Devil lye a few years back, now I use the large bags of lime.

If you definitely got your hands on 40lb bags of lye (sodium hydroxide) at Lowes, which section did you find it in?

Welcome to the forum by the way, it's great to have new members that are as safety conscience as you are!

Steve

 

[Oz]

Did you say you got 80lbs of lye (sodium hydroxide) at Lowes for $9.00?

Please check the bags to see what % and if it is indeed “sodium hydroxide”. If it is high purity there will be more than 1 member going to Lowes.

 

[2002valkyrie]

Valkyrie,

Are you sure you purchased lye, sodium hydroxide, and not lime, calcium hydroxide and magnesium hydroxide?

lazersteve, You are right, It is Lime not Lye don't know how I got that messed up. But if it'll work maybe I'll be o.k. Thank you for bringing that to my attention.

I plan to order from you on a regular basis in the future if all works out.

 

[Harold_V]

Valkyrie;

I assume that you already know that most of the experienced people on here consider lye to be more dangerous to the body than the strong acids normally used in home refining? :shock:

Protect your eyes (end everything else). 8)

Don

That's absolutely correct.
Years ago, I got a drop of nitric acid in my eye. A direct hit, a drop that bounced from a beaker as I was pouring from a container.

I was seconds away from fresh water, so it was quickly rinsed, but the damage was done. The surface of my eye turned yellowish and peeled off. I was alone, but could see well enough to find help in the yellow pages. I drove about five miles to an ophthalmologist, where I was treated. You may understand that I was very upset, thinking that I may lose the sight in the eye. The ophthalmologist was very reassuring, when he told me, and I quote, "you're very lucky it was acid instead of lye. The human body has the ability to neutralize acid, so while it does damage, it is limited. Your eye will be restored as it was, it just takes a few days. Had it been lye, you had but 15 seconds to eliminate it from your eye, which is not easily accomplished. Unlike acid, it continues to damage tissue, so had the drop been lye, you would have lost the sight in that eye".

Be very careful when handling lye----and wear the appropriate safety gear. Your sight relies on it.

Harold

 

[2002valkyrie]

On the other hand, Garden Lime shows to only have small amounts of Crystalline Silica which can be avoided with a good dust mask (I use a Dual Cartridge Respirator ) because airborne silica is baad for your lungs (lung disease & cancer).
So I will be doing the same as lazersteve.

 

[Harold_V]

About the door for the fume hood what would be a good material
I thought about window glass
Thanks

You might consider paying to have it tempered. Tempered glass is much tougher, and will not break into shards that can injure.

Harold

 

[butcher]

Have not followed thread closely, if using a plastic drum a window can be made from a plexiglass, easily shaped with heat. The window would not necessarily have to be in door, even maybe just a small window to peep inside, may all that is necessary. I like this Idea you brains are cooking up.

 

[dick b]

Hello again:

Yes your correct, the one I already have is similar to that one only smaller.

As long as the pH is maintained around 7 or neutral, then as the acid or base is absorbed, the fluid will move one way or the other way on the pH scale. The further it goes to 1 or 14 the more damage it will cause to the pump and seals.

So, by monitoring the pH level in the tank and adjusting to pH back to neutral the less damage to the pump will occur.

After you use the system for a time and learn how long it takes to change the pH and how much and how often you need to check it, the easier it will become to operate the system. If you're reacting with acids and you let the pH in the scrubber go to 1, it will stop absorbing the acid fumes from your exhaust and no scrubbing action will take place. The same is true for the opposite reaction if you're using bases for the reaction.

So for the system to operate properly, you have to monitor the pH level in the tank.

When all is said and done, you and I may find out that your original choice is the best one. When you develop a prototype, these are the things that you learn as you gain experience with what you're doing.

Good luck.
dickb

 

[goldbanger]

Does anyone have any ideas for using activated carbon to further return cleaner air?
I have fifty pounds of it and was wondering if it should be used before the scrubber or after?
I am making my setup out of polycarbonate (plexiglass) . I am thinking to use it after the scrubber.
any help would be awesome.
thanks,
harvey

 

[2002valkyrie]

Does anyone have any ideas for using activated carbon to further return cleaner air?
I have fifty pounds of it and was wondering if it should be used before the scrubber or after?
I am making my setup out of polycarbonate (plexiglass) . I am thinking to use it after the scrubber.
any help would be awesome.
thanks,
harvey

I just wish I had activated carbon, I'm using charcoal in a 6 gallon container after the scrubber before my 6 horse power shop vac. The scrubbed fumes are directed into the bottom of the container with the Vac hose at the top... I like it! There is no smell at all, even during the heavy work.


In my diagram I have a 55 gallon plastic drum for a work area (hood) the door is 1.5" from the bottom in case of spills, the exhaust is 3" pvc pipe and goes into a 3" x 4" elbow with a 4" pvc pipe going down 3' to a 4" elbow with 4" pipe 5' long, going to a 4" x 6" elbow with a 6" pvc pipe going up 4' with a 6 gallon bucket (with a hole in the bottom for the pipe) the 6" pipe pokes through the bottom of the bucket 2" and has 1" holes drilled around the side of the pipe. Inside the bucket is the bottom 3" of a 5 gallon bucket upside down over the pipe (1/2" holes in it random but not over the pipe) Charcoal in the 6 gallon bucket on top of the 5 gallon bottom. A 6 hp shop vac hose is attached to the top of the 6 Gallon charcoal bucket. There is 6" of lye water in the pvc pipe (this was optimal for this set up) remember to put a ball valve on the lowest point for drain purposes (lowest point for gold recovery) The shop vac is not permanently mounted so it can be removed any time it is needed else where.

 

[4metals]

Any idea what the CFM rating of this blower is? Your hood should have 100 cfm for every square foot of opening. That will give you enough exhaust to keep the air flowing away from your face.

The thing you're looking for to adapt a round duct to a square hole is called a transition flange, try US Plastics

 

[4metals]

100 CFM per sq ft of opening is a rule of thumb. By the way consider using make up air to minimize removing the air conditioned or heated air from your lab. It's hard to keep a room warm in winter (or cool in summer) when you exhaust thousands of cubic feet per minute.

US Plastics was only suggested so you can go on line and see one, I'm sure they're available down under as well. It helps to know what they're called and what they look like.

 

[goldsilverpro]

The 100 cfm/square foot of hood opening is also the same rule I've used all my life.

 

[eeTHr]

Here is a suggestion: Turn your system on, put a small Corningware casserole dish, about 6" x 6", in there, and pour about 1/4 inch of HCl into it. Open the HCl inside the hood, and re-cap it inside the hood.

If you don't smell anything at this point, it's sucking air pretty good.

Walk down wind of your exhaust. If you don't smell anything, the neighbors won't either. Either you are scrubbing most everything out of the hood air, or it's dissipating in the outside air.

A further test would be to add about a teaspoonfull of nitric to the HCl, opening and closing the nitric container inside the hood. Do the smell tests again.

Put a small piece of base metal into the casserole. Do the smell tests again.

Heat the casserole in the hood. Do the smell tests again.

This should give a good indication, with relatively little risk.

If you reeeeeealy want to know how much scrubbing you've got, tape or hold a litmus strip at the exhaust opening for 60 seconds, and see what it does. I don't know how to interpret that into ppm or anything, but it would give you some general idea.

Unless you will have the EPA testing it, the amount of reduction of fumes you need is up to you and your neighbors' sense of smell, and the surrounding metallic property.

That's just my opinion, though.

 

[qst42know]

There must be something extra that those balls can do
maybe they can mix the water better

Lots of surface area with no dead space.

 

[golddie]

http://www.jaeger.com/tripack.htm
I just picked up these things and I paid 340 dollars and this will be enough for my scrubber.
The person made a mistake when he said 1,200 dollars.
He said he sells these things to fish farms.

 

[Barren Realms 007]

The nozzles in the top of the column spray the solution, the solution trickles down over the media and mixes with the fumes or material from you scrubber to neutralize it. There should not be much if any fluid that collects in the bottom of your scrubber that should be held in your tank that your pump pulls your solution from.

 

[4metals]

The balls should have a surface film of water on them to work effectively. This is accomplished by pumping the scrubbing liquid through the nozzles over the bed of packing. The water level in the sump should not be so high as to submerge any of the packing. The air water interface is where the reaction happens.

As far as determining how much packing is needed the question being asked should be the CFM going through the scrubber. (which is not necessarily the CFM of the blower, it depends on your ducting) The longer the fumes remain in the working area of the scrubber (the wetted packing) the more effective the scrubber.

 

[PreciousMexpert]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776
In this picture the fumes are going into the water.
I am not sure if this is right or the water level should not be so high.
I thought the media should not touch water.

 

[4metals]

The fumes are not going into the water, the height the fume enters the scrubber is higher than the tank that holds the water. If those fumes are going into water the room has 2 feet of water in it!

The fume enters under the grating that holds the packing, that is not the water level. This allows the fume to disperse and fill the column as it rises.